It is actually a chemical in the brain that creates the sensation of eating enough, a chemical that is depleted by consuming simple sugars.
POE:
(A) seems good. Hold it.
Eliminate (B) - 'which' is referring to brain instead of chemical.
Eliminate (D) & (E) - 'Actually' is changing the implied meaning. Also, in (E) verb incorrect.
Down to two (A) & (C)
Though (C) is passive but it is simple and clear as compared to (A)(A) It is actually
a chemical in the brain that creates the sensation of eating enough,
a chemical that is
(B) It is actually a
chemical in the
brain which create the sensation of eating enough, a chemical which is
(C) The sensation of having eaten enough is actually created by a chemical in the brain that is -
CORRECT(D) A chemical
actually creates the sensation in the brain of having eaten enough, and
this chemical is
(E) A chemical
actually create the sensation in the brain of having eaten enough, and
that chemical is